1996 - 2016
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...
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This collection of video and a few audio files represents files that have been featured on the RF Cafe homepage. Every week or so a new file is added that should be of interest to RF Cafe visitors.
Please send me an e-mail if you have a good subject. Note: "Videos for Engineers" formerly went by the name "Cool Videos."
advantage for me of having a hobby like radio control models is that since wireless technology is used for
commanding the airplane, helicopter, boat, car, etc., any interesting application qualifies as a legitimate
topic for RF Cafe articles. Such it is for this video of an R/C Superhero (formally spelled "RcSuperhero") model
designed and built by Greg Tanous, of Portland, Oregon. The model shown is 78 inches tall, has a 47" wingspan
(armspan) weighs about 3.3 pounds, and is propelled by a high-power brushless motor that generates more than 5
pounds of thrust; that is why RcSuperhero is able to take off straight up. Carbon fiber spars are used to
stiffen the foam structure. Radio control is via a spread spectrum system that operates on the license-free 2.4
GHz ISM band (although a 72 MHz FM system would work equally well). According to Greg, RcSuperhero builds and
flies as easily as an advanced trainer. Plans and entire kits for this 78" tall version and a 57" tall version
can be ordered from his...<more>
Is this the future of construction? In this video, wirelessly controlled flying robots carry building blocks to the work site and, after precisely positioning the block, plunks it into place. It then flies off to pick up and place the next block. Multiple builder bots are in operation simultaneously. A 20-foot tall model (1:100) of a modularized human habitat structure - a "vertical village" - was constructed automatically using 1,500 polystyrene blocks. A sophisticated algorithm defined not just the construction sequence and geometry, but also handled traffic patterns, collision avoidance with other vehicles and the structure itself, and maximized system efficiency. ETH Zurich roboticist Rafaello D'Andrea and architects Fabio Gramazio and Matthias Kohler are the progenitors and implementers of this amazing demonstration. BTW, the hissing sound in the background is a painter spraying the blocks white.
How much does the Internet weigh? That is the question posed and answered in this video that has been making the rounds in the last couple weeks. Vsauce's Michael, who has produced many really good science-related short videos, explains how to calculate the weight of all the information residing on the Internet based on the weight of electrons necessary to transport the data. The sum: 50 grams - about the weight of a strawberry. Those 50 grams worth of electrons represent an estimated 5 exabytes (5 million terabytes). Furthermore, Michael calculates that all of the actual information contained in pictures, e-mail, websites (like this one), movies, documents, etc., in terms of electron mass, would fit on the head of a pin. Of course in the condensed state all information would be lost because it would have no structure, so the exercise is purely academic.
11/8/2011What you are seeing is the automated production of contraband that could result in heavy fines and possible imprisonment if sold here in the United States after January 1, 2012. It's not a meth lab or an unauthorized replica of the iPhone 4. What is it, then? Website visitor Hugh P. sent me a link to this video showing the production line for Duro-Test's (nope, I've never heard of 'em either) 100-W, 120-V incandescent light bulbs. The ingenuity needed to conceive of and implement the machinery and controllers for as relatively simple a product as a light bulb is utterly impressive. Note how robust everything is and that most of it is metal, something maybe not expected for machinery that handles delicate glass shells and forms ultrafine filament wires. This is the kind of skill that built the modern world and is the result of lots of trial and error, success and failure. Capitalism motivated the business owners, engineers, managers, production workers, and ultimately the salesmen to believe the effort would be worth it. They busted their posteriors. OWS rats thinks all of this result of other people's work should be made available for free to them, most of whom have never produced anything but the need for toilet paper.
Cloaking has been a big deal since Star Trek made the concept part of the household lexicon. This video demonstrates the principle described in a paper titled, "Mirage Effect from Thermally Modulated Transparent Carbon Nanotube Sheets." Per the paper, "The single-beam mirage effect, also known as photothermal deflection, is studied using a free-standing, highly aligned carbon nanotube aerogel sheet as the heat source. The extremely low thermal capacitance and high heat transfer ability of these transparent forest-drawn carbon nanotube sheets enables high frequency modulation of sheet temperature over an enormous temperature range, thereby providing a sharp, rapidly changing gradient of refractive index in the surrounding liquid or gas." BTW, forest-drawn means a sheet of vertical nanotubes standing like trees in a forest.
Even if you have taken some pretty intense physics courses in college, this series of short videos (a minute long) will really appeal to you. In a mesmerizingly primal manner, the lessons are conducted with a voice narrating while a hand draws simple diagrams to compliment the story. I am amazed to witness how consistently each concept is presented in utter simplicity - sort of a validation of Occam's razor. The first one I watched was on the speed of light in glass, and why frequency stays the same even though the speed of light is lower in glass. The explanation of distance measurement from a Special Relativity might surprise you from a time perspective that you hadn't considered before. Check out similarly creative lessons on the Heisenberg Uncertainty Principle, the arrow of time, Schrödinger's Cat, and many more.
can buy you a lot of publicity - the more extreme, the better. I remember when the ground fault circuit
interrupter (GFCI) was first introduced to the market, a VP of some manufacturer (GE?) grabbed a radio that was
plugged into a GFCI receptacle and jumped into a pool with it. He lived, and everybody trusted GFCIs forever
ioSafe, maker of "disaster-proof hardware," adopted a
similar marketing strategy by subjecting its Go-Anywhere hard drive to the discharge of a 1 MV Tesla coil. In
this demonstration filmed by MSNBC, CEO Rob Morris narrates while an expendable employee dons a Faraday suit,
complete with a real bird cage for a hood, and holds the Go-Anywhere up to the Tesla coil to invoke its wrath of
fiery discharge. Reporterette Rosa Golijan then connects the HDD to her laptop computer to test whether it is
indeed immune to "thunder bolts" (her term). Oops, it didn't work. Rather than being an upset for the team
though, Mr. Morris proceeded to demonstrate his company's other forte - data recovery. He opened the HDD (no ESD
protection worn, BTW), connected an interface board, and was able to read the drive content. Watch the video to
see a surprise at the end.
It's the time of year once again where much of the world celebrates Christmas or Hanukkah either as religious or happy secular holidays. So, every year I offer a collection of music videos that my family particularly enjoys, especially ones with kids singing. Hopefully you will as well. In spite of politically correct efforts to suppress and erase the traditions, here at RF Cafe I have never been one to yield to such bigotry. Don't be offended; be tolerant. Merry Christmas to all, and to all a good night.
If the generals and insane leader of an unfriendly nation knew that the country they were provoking had the capability to drop a significant tonnage of explosives on their heads in an hour or less, would that serve as a deterrent? News wires recently reported on a successful test of the USAF's Falcon Hypersonic Technology Vehicle (HTV) that has such a potential. The first test a couple months ago ended in failure, but evidently the kinks have been worked out. According to DARPA's website, "Falcon HTV-2 is an unmanned, rocket-launched, maneuverable aircraft that glides through the Earth’s atmosphere at incredibly fast speeds—Mach 20 (approximately 13,000 mph). At HTV-2 speeds, flight time between New York City and Los Angeles would be less than 12 minutes. The HTV-2 vehicle is a 'data truck' with numerous sensors that collect data in an uncertain operating envelope." <more>
The Japanese have been way ahead of the curve in the robot world for many years. Combining autonomy with wireless control has led to this "Spherical Flying Machine" that was demonstrated by the Japan Ministry of Defense. Beginning with a dose of theatrical showmanship, the mystery craft jumps out of a round Styrofoam container after the lid is suddenly popped off. What emerges is a very obviously highly stable and maneuverable sphere that effortlessly floats above the stage and audience, while intermittently flitting about like a dragonfly moving along the shoreline from cattail to cattail. Multiple onboard gyroscopes provide attitude control and stability so effective that even after being hit or pushed, it rights itself. Flying is not its only method of locomotion; once on the ground the spherical flying machine becomes the spherical rolling machine. It can also hug a wall near the ceiling and navigate through a building. This allows it to be used for surveillance in almost any environment. Its quite electric motors, most likely powerful, microprocessor-driven brushless models given life by high-C lithium polymer batteries, provide plenty of motivational force. A 2.4 GHz radio control system was used for guidance. Come to think of it,...<more>
"A Ham's Night Before Christmas," by Gary Pearce, KN4AQ, was first posted on YouTube in November of 2011. This clever adaptation of Clement Clark Moore's familiar story Twas the Night Before Christmas. The narration is accompanied by pictures of vintage magazine covers, advertisements, and cartoons. It opens with the cover of the December 1920 edition of QST (first edition ever printed was December of 1915). Here are the first couple verses, as discovered on Brainerd Area Amateur Radio Club website. Please visit them for the rest of the poem, as well as other versions written by various authors. All are very clever. <more>
As with amateur radio hobbyists who continually help advance the state of the art in electronics, software, and communications, so too do model aircraft hobbyists help push back the frontiers of ignorance in their realm. Guys like Tom Mast, a Staff Engineer with Bell Helicopter Textron, are part of a fairly elite cadre of people with an ability to integrate a large collection of skills into a single sophisticated project. Knowledge of rotorcraft and fixed wing aerodynamics, propulsion system mechanical and electrical requirements, microcontroller programming, structure weight-strength tradeoffs, materials science, design-for-production aspects, and the skill to fly both fixed and rotor wing models were necessary to pull this off. I have not found any detailed history on the development, but about three years of dedicated effort was required from concept to reality. As you can <more>